1. Field of the Invention
The present invention relates to final drive units of vehicular drive axle assemblies and, more particularly, to a lubrication arrangement for use in the final drive unit which can provide good lubrication of bearings supporting a pinion drive shaft within a carrier housing of the vehicular drive axle assembly even when a vehicle body is in an inclined state.
2. Description of the Prior Art
Conventionally, final drive units well known in the prior art, are arranged in a power transmission system of a motor vehicle to allow a pair of output shafts operatively coupled to a propeller shaft.
The typical lubrication apparatus used in the final drive unit for motor vehicles includes a carrier elongated in a fore-and-aft direction of the motor vehicle and receiving lubricating fluid, a differential case arranged at a rear end of the casing, a differential gear unit rotatably disposed within the differential case, a drive gear mounted to the differential case, and a drive pinion shaft that is formed with a drive pinion meshing with the drive gear. The drive pinion shaft is elongated forward to be connected with a front-wheel side trans-axle via a propeller shaft. The drive pinion shaft is rotatably supported by a pair of axially spaced outer and inner tapered roller bearings. With this arrangement, when the motor vehicle is in a normal horizontal position, the roller bearings are immersed in the lubricating fluid to be sufficiently lubricated. Typically, the outer bearing pumps the lubricating oil into a cavity between the two bearings. This pumping action allows the outer bearing which is subject to the larger amount of drive torque to be well lubricated. However, when the motor vehicle runs on a decent and/or ascent, the lubricating oil is not getting to the bearings due to gravity. In this situation the lubricating oil must be pushed up hill to the space between the outer bearing and a seal. The lack of the lubricating oil necessary for positive lubrication of the roller bearings, especially acute at low speed of the motor vehicle, may be very detrimental for the bearings of the final drive unit.
Accordingly, it is the intent of this invention to overcome these shortcomings of the prior art.